The accident took place in Kulekhani village in Makwanpur district.
Two persons died on the spot and another succumbed to injuries while undergoing treatment in a hospital in the capital, according to police.
The dead have been identified as Ghanshyam Prasad (60) and Deviyanti Devi (63), both members of a family from Ranchi who were going to Kathmandu.
"The jeep with the Indian registration number fell around 200 metres down the road at around 4 pm today," police said.